UNIT 1 & 2 PART A 1. Identify the role of a CA. 2. Draw the architecture of Single Homed Bastion. 3. What is DMZ? 4. List out the seven group documents describing the set of IPSec Protocols. 5. Define Security Associations. 6. Draw the structure of DES–EDE3–CBC algorithm. 7. Draw the structure of MIME Header. 8. Define VPN 9. What is Dual Signature and Signature verification? 10. List out the seven group documents describing the set of IPSec Protocols. 11. Identify the roles of a firewall. 12. Define Security Associations. 13. Diagrammatically represent IPSec documents 14. Derive an equation to compute HMAC over a message. 15. How is the Master Secret Computed? 16. Diagrammatically represent the packet structure of ESP Transport mode for IPv4 17. HMAC provides data integrity. Justify 18. How to convert the Master Secret into Key Block? PART B 1. Explain the importance of Key Management Protocol for IPSec and its working in detail. 2. Explain the Pseudo Random function and HMAC algorithm of TLS. 3. Discuss about the header format of MIME and explain its working. 4. Examine the various types of Firewalls and discuss about their architecture in detail. 5. Compose a method to compute the Master Secret and convert the Master Secret into Cryptographic Parameters 6. Explain how Radix-64 conversion takes place in PGP with an example. 7. Design a model to process cryptographic computations in TLS and discuss about the Error Alerts given by TLS. 8. Explain the importance of Key Management Protocol for IPSec and its working in detail. 9. Discuss about the PGP Message Format and explain its working. 10. Examine the various Firewall designs and discuss about their architecture in detail. 11. Discuss in detail how the Security Association are implemented. Support your explanation with an overview about IPSec Protocol documents 12. Explain how Authentication and Confidentiality is provided by PGP with an example.
CS6551-Computer networks Department of CSE 2014-2015 UNIT I FUNDAMENTALS & LINK LAYER PART A 1. Compare LAN and WAN. Local Area Network (LAN) Wide Area Network (WAN) Scope of Local Area Network is restricted to a Scope of Wide Area Network spans over large small/ single building geographical area country/ Continent LAN is owned by some organization. A part of network asserts are owned or not owned. Data rate of LAN 10-100mbps. Data rate of WAN is Gigabyte. 2. Define Full Duplex and simplex transmission system. With Full duplex transmission, two stations can simultaneously send and receive data from each other. This mode is known as two-way simultaneous. The signals are transmitted in only one direction. One is the sender and another is the receiver. 3. Why sliding window flow control is considered to be more efficient than stop and wait flow control? In sliding window flow control, the transmission link is treated as a pipeline that may be filled with frames in transit. But with stop-and-wait flow control only one frame may be in the pipe at a time. 4. Differentiate between lost frame and damaged frame? Lost Frame Damaged Frame Lost frame is the frame that fails to arrive at the The damaged frame is a recognizable frame other side. does arrive, but some of the bits are in error 5.What is the difference between stop and wait and sliding window protocol? (Nov/Dec 2012) Stop and Wait Protocol Sliding Window Protocol In stop and wait protocol, we can send one In sliding window protocol we can send frame at a time multiple frames at a time. Shows poor performance than Sliding Window As sliding window doesn't waste network Protocol, comparatively bandwidth compared with stop-n-wait window shows better performance than stop-n-wait. 6. Define Piggybacking? The technique of temporarily delaying outgoing acknowledgment so that they can be hooked onto the next outgoing data frame is widely known as piggybacking. 7. What is OSI? OSI (Open Systems Interconnection) is reference model for how applications can communicate over a network. It is partitioned into seven layers. It was developed by the International Organization for Standardization (ISO). 8. What is a protocol? What are the key elements of a protocol? Protocol is used for communications between entities in a system and must speak the same language. Protocol is the set of rules governing the exchange of data between two entities. It defines what is communicated, how it is communicated, when it is communicated. The Key elements of a Protocol are • Syntax – It refers to the structure or format of data meaning the order in which they are presented. • Semantics – It refers to the meaning of each section of bit. How to do interpretation. • Timing – When data should be sent and how fast they can be sent. 9. What are the uses of transport layer? • Reliable data exchange • Independent of network being used • Independent of application 10. What is Protocol Data Unit (PDU)? At each layer, protocols are used to communicate and Control information is added to user data at each layer. Transport layer may fragment user data. Each fragment has a transport header added and header consists of destination SAP, sequence number and error detection code. 11. What are the uses of internet layer in TCP/IP? • Systems may be attached to different networks • Routing functions across multiple networks
CS6551-Computer networks Department of CSE 2014-2015 • Implemented in end systems and routers 12. What is a layered Network Architecture? • A layer is created when a different level of abstraction occurs at protocol. Each layer should perform a well defined function. • Function of each layer should be chosen using internationality standardized protocols. Boundaries between should be chosen to minimize information flow across the interfaces. • A set of layers and protocol is called network architecture. A list of protocols used by a system is called protocol stack. 13.Compare OSI and TCP. Open System Interconnection(OSI) Transmission Control Protocol(TCP) It distinguishes between Service, Interface, It does not distinguish between Protocol Service,Interface,Protocol Protocols are well hidden Protocols are not just hidden Dejure standard Fit Model Defacto standard Fit Model In transport layer only connection oriented In Transport layer choice is for connection services are available oriented and connectionless Contains 7 layers Contains 5 layers 14. How do layers of the internet model correlate to the layers of the OSI model? OSI TCP/IP Physical Layer Physical Layer Data Link Layer Network Access Layer Network Layer IP Layer Transport Layer TCP Layer Session Layer Application Layer Presentation Layer Application layer 15. What is the use of data link layer in OSI? • Frame synchronization: Data is divided by data link layer as frames, a manageable unit. • Flow Control: Sending station does not overwhelm receiving station. • Error Control: Any error in bits must be detected and corrected using some mechanism. • Addressing: Two stations in a multi point that involved in transmission must be specified using physical address • Access Control: When two or more devices are connected to the same link, Access control mechanism is needed to determine which device has control over the link at any given time. 16. Why is flow control and error control duplicated in different layers? Like the data link layer, the transport layer is responsible for flow and error control. Flow control and error control at data link layer is node-to-node level. But at transport layer, flow control and error control is performed end-end rather than across a single link. 17. List the key ingredients of technology that determines nature of a LAN. List the common topologies available for LAN. Topology, Transmission medium and Medium access control technique are the technology that determines nature of a LAN. Star Topology, Ring Topology, Bus Topology and Tree Topology are the topologies available for LAN. 18. What are the functions of physical layer and presentation layer? Functions of Physical Layer • Encoding/ decoding of signals • Preamble generation/removal (for synchronization) • Bit transmission/ reception Functions of Presentation Layer • Translation, Encryption / Decryption ,Authentication and Compression 19. What do you mean by Flow Control? (Nov/Dec 2011, May/June 2015) Flow control is a technique for assuring that a transmitting entity does not overwhelm a receiving entity with data. It is a feedback mechanism by which the receiver is able to regulate the sender. Such a
CS6551-Computer networks Department of CSE 2014-2015 mechanism is used to keep the sender from overrunning the receiver, i.e., from transmitting more data than the receiver is able to process 20. Define error detection and correction. (Nov/Dec 2011) Error detection: Sender transmits every data unit twice. Receiver performs bit-by-bit comparison between that two versions of data. Any mismatch would indicate an error, which needs error correction. Error Correction is the process or analyzing and rectifying the errors and the code. 21. What are the functions of Application Layer? (Apr/May 2011) It enables the user (human/software) to access the network. It provides user interfaces and support for services such as electronic mail, remote file access and transfer, shared database management and other types of distributed information services. Services provided by the application layer are Network Virtual terminal, File transfer, access and management. Mail services, Directory services. 22. Define bit stuffing. (Apr/May 2011) HDLC denotes both the beginning and the end of a frame with the distinguished bit sequence 01111110. This sequence might appear anywhere in the body of the frame, it can be avoided by bit stuffing. On the sending side, any time five consecutive 1’s have been transmitted from the body of the message (i.e., excluding when the sender is trying to transmit the distinguished 01111110 sequence), the sender inserts a 0 before transmitting the next bit. 23. What are the two types of line configuration? (Nov/Dec 2010) The two types of line configuration are Point to point line configuration and multipoint line configuration. Point to point line configuration • It provides a dedicated link between 2 devices. • Entire capacity of the link is reserved for transmission between 3 devices only Eg: connection between remote control and TV’s control system Multipoint line configuration • Also called as multi drop connection • Here the channel capacity is shared • If many devices share the link simultaneously it is called spatially shared connection 24. What do you mean by error control? (Nov/Dec 2010, May/June 2015) Error control refers to mechanism to detect and correct errors that occur in the transmission of frames. 25. What are the major duties of Network Layer? (May/June 2012) It is used to send the data from source to destination with help of logical address. 25. What are the two types of errors occurred during data transmission? (May/June 2012) Single bit error and burst error 26. Define networks.(Nov/Dec 2012) A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. Networks are commonly categorized based on their characteristics. 27. Compare error detection and correction. (Nov/Dec 2012) Error Detection Error Correction Only the occurrence of an error is checked The exact number of bit that are corrupted and location of error in the message are known. Error detecting code is to include only enough Error correcting code is to include redundant redundancy to allow the receiver to deduce information along with each block of data sent that an error occurred but not which error and to enable the receiver to deduce what the have it request a re-transmission. transmitted character must have been Basically four methods-VRC,LRC,CRC and Hamming code Checksum PART-B 1. Explain in detail the error detection. (Nov/Dec 2010, Apr/May 2012, Nov/Dec 2012) 2. Explain about internet architecture. (May/June 2015) 3. Discuss in detail about the layers in OSI model. (Nov/Dec2010, Nov/Dec2011, Apr/May2012, Nov/Dec 2012) 4. Explain sliding window flow control and stop and wait flow control in detail.